The Experts below are selected from a list of 165 Experts worldwide ranked by ideXlab platform
Jeffrey L Bada - One of the best experts on this subject based on the ideXlab platform.
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The Urey Instrument: An Advanced In Situ Organic and Oxidant Detector for Mars Exploration
Astrobiology, 2008Co-Authors: Andrew D. Aubrey, Jeffrey L Bada, John H. Chalmers, Frank J. Grunthaner, Xenia Amashukeli, Peter A. Willis, Alison M. Skelley, Richard A. Mathies, Richard C. Quinn, Aaron P. ZentAbstract:The Urey organic and oxidant detector consists of a suite of instruments designed to search for several classes of organic molecules in the martian regolith and ascertain whether these compounds were produced by biotic or abiotic processes using chirality measurements. These experiments will also determine the chemical stability of organic molecules within the host regolith based on the presence and chemical reactivity of surface and atmospheric oxidants. Urey has been selected for the Pasteur payload on the European Space Agency's (ESA's) upcoming 2013 ExoMars rover mission. The diverse and effective capabilities of Urey make it an integral part of the payload and will help to achieve a large portion of the mission's primary scientific objective: “to search for signs of past and present life on Mars.” This instrument is named in honor of Harold Urey for his seminal contributions to the fields of cosmochemistry and the origin of life.
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state of the art instruments for detecting extraterrestrial life
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Jeffrey L BadaAbstract:“Surely one of the most marvelous feats of 20th-century science would be the firm proof that life exists on another planet. In that case, the thesis that life develops spontaneously when the conditions are favorable would be far more firmly established, and our whole view of the problem of the origin of life would be confirmed.” Stanley Miller and Harold Urey wrote that in 1959 (1). Unfortunately, their dream has not been realized, and as we begin this new millennium the question of whether life exists beyond the Earth remains unanswered. However, there are reasons for optimism that in the not-too-distant future we may have an answer.
Derek W. G. Sears - One of the best experts on this subject based on the ideXlab platform.
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Oral Histories in Meteoritics and Planetary Science—XXI: Donald Burnett
Meteoritics & Planetary Science, 2013Co-Authors: Derek W. G. SearsAbstract:In this interview, Donald Burnett (Fig. 1) describes how he applied to the University of Chicago, with considerable support from his father, where he took classes from Harold Urey and was inspired by Ed Anders to pursue a career in nuclear chemistry and, later, cosmochemistry. As a graduate student at the University of California at Berkeley, Don learned to use charged-particle tracks as a detector for radioactive nuclei, a technique that he applied to a wide variety of problems over the next 20 years, including the neutron profile probe that was deployed on the Moon. After a one-year postdoc with William Fowler at the California Institute of Technology, he became involved with Jerry Wasserburg, who ultimately obtained a faculty position for him in the Geology Division. Since then, Don has worked on a number of fundamental problems in cosmochemistry, chronology of the solar system, the initial Pu/U abundance, fractionation of U and Pu in igneous processes, and elemental abundances. This last interest led him to advocate, propose, and lead the Genesis space mission to collect and return samples of the solar wind. The crash of the return capsule caused alarm, but some aspects of the mission were unaffected and others have been successfully handled, so that several major new results have been published: the lack of an SEP component in lunar samples, the Ne and Ar composition of the solar wind, and, most importantly, the oxygen and nitrogen isotopic composition of the Sun. Don received the Leonard Medal in 2012.
Aaron P. Zent - One of the best experts on this subject based on the ideXlab platform.
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The Urey Instrument: An Advanced In Situ Organic and Oxidant Detector for Mars Exploration
Astrobiology, 2008Co-Authors: Andrew D. Aubrey, Jeffrey L Bada, John H. Chalmers, Frank J. Grunthaner, Xenia Amashukeli, Peter A. Willis, Alison M. Skelley, Richard A. Mathies, Richard C. Quinn, Aaron P. ZentAbstract:The Urey organic and oxidant detector consists of a suite of instruments designed to search for several classes of organic molecules in the martian regolith and ascertain whether these compounds were produced by biotic or abiotic processes using chirality measurements. These experiments will also determine the chemical stability of organic molecules within the host regolith based on the presence and chemical reactivity of surface and atmospheric oxidants. Urey has been selected for the Pasteur payload on the European Space Agency's (ESA's) upcoming 2013 ExoMars rover mission. The diverse and effective capabilities of Urey make it an integral part of the payload and will help to achieve a large portion of the mission's primary scientific objective: “to search for signs of past and present life on Mars.” This instrument is named in honor of Harold Urey for his seminal contributions to the fields of cosmochemistry and the origin of life.
Donald L. Turcotte - One of the best experts on this subject based on the ideXlab platform.
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Carbonation and the Urey reaction
American Mineralogist, 2019Co-Authors: Louise H. Kellogg, Harsha Lokavarapu, Donald L. TurcotteAbstract:Abstract There are three major reservoirs for carbon in the Earth at the present time, the core, the mantle, and the continental crust. The carbon in the continental crust is mainly in carbonates (limestones, marbles, etc.). In this paper we consider the origin of the carbonates. In 1952, Harold Urey proposed that calcium silicates produced by erosion reacted with atmospheric CO2 to produce carbonates, this is now known as the Urey reaction. In this paper we first address how the Urey reaction could have scavenged a significant mass of crustal carbon from the early atmosphere. At the present time the Urey reaction controls the CO2 concentration in the atmosphere. The CO2 enters the atmosphere by volcanism and is lost to the continental crust through the Urey reaction. We address this process in some detail. We then consider the decay of the Paleocene-Eocene thermal maximum (PETM). We quantify how the Urey reaction removes an injection of CO2 into the atmosphere. A typical decay time is 100 000 yr but depends on the variable rate of the Urey reaction.
Melissa Lee Phillips - One of the best experts on this subject based on the ideXlab platform.
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The Origins Divide: Reconciling Views on How Life Began
BioScience, 2010Co-Authors: Melissa Lee PhillipsAbstract:F our and a half billion years ago, the planet Earth coalesced out of the gas and dust left over from the formation of the sun. For the next several hundred million years, the young planet was bombarded by comets and meteorites, volcanic eruptions raged across its surface, and its heat boiled the nascent oceans. But within about a billion years—and perhaps much earlier—life had arisen. How nonliving chemicals transformed into living molecules is one of the biggest mysteries in science, and we might never know for sure how it happened. Deep divides in opinion are found in almost all areas of origin-of-life research. Did life begin in extreme heat or relative cold? Were its essential molecules synthesized in the prebiotic ocean, at the mouths of churning deep-sea vents, or did they rain down from space? Did the first life-form get its energy from the sun or from the chemical energy of minerals? Were inherited genetic molecules essential to the first life-form, or could life simply have been a chain of chemical reactions taking place on a rock? “If we’re going to make any progress, we really have to be critically life couldn’t arise out of nothing, then where did it come from? A few years later, Darwin speculated about chemical reactions in a “warm little pond,” and Alexander Oparin and J. B. S. Haldane independently took that idea a step further by proposing that life began in a primordial ocean of organic molecules. Origin-of-life research didn’t get its experimental start, however, until the famed chemical synthesis experiments of Stanley Miller and Harold Urey, of the University of Chicago, were published in 1953. By sending an electrical current through a mixture of water, methane, ammonia, and hydrogen, they simulated what might have happened when lightning struck the oceans and atmosphere of ancient Earth. What they got—a mixture of key amino acids and other organic molecules—profoundly changed views of the origin of life. The origin of biology was now experimentally approachable. Other groups soon conducted similar experiments, and in the following years, researchers managed to synthesize not only additional amino acids but also other essential biomolecules, including sugars, metabolic acids, and lipids. honest about what we don’t know,” says geochemist George Cody, of the Carnegie Institution for Science in Washington, DC. “And that’s just about everything.” The questions surrounding life’s origins are indeed vast and, for the most part, unanswered. A comprehensive explanation of the origin of life will require pinning down the beginnings of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), of proteins and lipid membranes, of genetic coding and metabolic machinery. In modern life, all of these molecules and processes are so intertwined that it’s difficult to imagine how any of them could have arisen without the others already in place. Chicken-andegg problems abound. But new technologies, hypotheses, and experiments are constantly surfacing, and each step reveals a bit more of the way the inanimate chemistry of Earth’s beginnings may have morphed into the remarkable variety of life we see today.
